(Not Applicable)
1. Field of the Invention
This invention relates generally to chemical, geological, and photosynthetic sequestration of CO2, pollution control systems, and particularly to a method for removal of CO2, CO, NOx, and SOx emissions, for reduction of NO3xe2x88x92 contamination of surface water and groundwater, and for sequestration of inorganic carbon into soil and subsoil earth layers.
2. Description of the Relevant Art
The rise in anthropogenic greenhouse gas emissions, particularly CO2, is attributed largely to the increased use of fossil fuels. Fossil fuels, particularly coal, oil, and natural gas, are the primary fuels of industrialized society. These fuels supply abundant energy at low cost. Currently 22 gigatons (Gt) of CO2 per year (equivalent to 6 Gt C/yr) is emitted as a result of the use of fossil fuels. Coal is the fuel most widely used for the generation of electricity worldwide because it is readily available, easily transportable, and relatively inexpensive. Approximately 70% of all the electricity used in the United States is generated from coal and natural gas. Oil-derived products dominate transportation fuels. Worldwide, coal-fired power plants result in about 1.8 of the 6 Gt C/yr of CO2 emissions. The remainder is from the use of fossil fuels in transportation, industry, and residences.
The increasing effects of CO2 emissions and global warming have challenged the industrialized world to find new and better ways to meet the increasing need for energy while reducing greenhouse gases. A treaty recently negotiated in Kyoto, Japan, would require developed nations to reduce their emissions of greenhouse gases below 1990 levels by the year 2010. New strategies for economically controlling the emissions of greenhouse gases are therefore required.
The process of photosynthesis removes more CO2 from the atmosphere than any other reaction. Each year, land-based green plants remove about 403 Gt CO2 (equivalent to 110 Gt C) from the atmosphere and the oceans draw approximately 385 Gt CO2 as well. An enhancement as small as 6% for terrestrial or ocean photosynthesis is sufficient to remove 22 Gt CO2 (6 Gt C), or the entire amount of CO2 emitted into the atmosphere annually from the use of fossil fuels. The requirements of the recent Kyoto Treaty could be satisfied by an increase of only 0.62% in annual global photosynthetic biomass production, if the increased biomass is in a stable form such as woody products.
In many parts of the world, land-based photosynthesis in the form of crop production is limited by the lack of fertilizers. Nitrogen in the form of ammonium, NH4+, is the most-needed fertilizer since it is an essential substrate for the synthesis of all amino acidsxe2x80x94and thus proteins, chlorophyll, and many lipid molecules of membranes. All are important components of photosynthetic membranes. An increase in the use of fertilization can dramatically enhance photosynthetic activity by stimulating more green plants to grow. This would result in the capture of more sunlight energy and the fixation of more CO2. A more abundant supply of environmentally friendly fertilizers and appropriate fertilization of trees can be a positive contribution to global CO2 sequestration.
According to the invention, industrial combustion facilities can be integrated with greenhouse gas-solidifying fertilizer production reactions so that CO2, CO, NOx, and SOx emissions are converted into carbonate-containing fertilizers, primarily NH4HCO3 and (NH2)2CO, that can enhance the sequestration of CO2 into soil and the earth subsurface, reduce the problem of NO3xe2x88x92 runoff, and stimulate photosynthetic fixation of CO2 from the atmosphere. Therefore, CO2 emission sources, such as from a fossil fuel-fired power plant, are directed to a reactor before they can be emitted through smokestacks. In the reactor, CO2 is converted to at least one selected from the group consisting of NH4HCO3 and (NH2)2CO. The NH4HCO3 and/or (NH2)2CO is then applied into soil to enhance carbonization of soil and subsoil earth layers and to stimulate photosynthetic fixation of CO2 from the atmosphere.
The production of NH4HCO3 and (NH2)2CO is summarized by the reactions:
2CO2+N2+3H2+2H2O xe2x86x922NH4HCO3↓
CO2+N2+3H2xe2x86x92(NH2)2CO↓+H2O
Methane (CH4) and/or carbon monoxide (CO) can be utilized instead of hydrogen gas according to the following reactions:
5CO2+4N2+14H2O+3CH4xe2x86x928NH4HCO3↓
CO2+4N2+2H2O+3CH4xe2x86x924(NH2)2CO↓
3CO+N2+5H2Oxe2x86x922NH4HCO3↓+CO2
The invention is also useful for removing NOx and SOx emissions by the following reaction pathway: 
wherein R is at least one selected from the group consisting of CO, H2 and CH4.
Catalysts are used to catalyze the reactions of the invention. Preferred catalysts include, but are not limited to, nanometer-structured and/or hybridized metallocatalysts of Ru, Os, W, Fe, Pt, Pd, and Ni.
Important features and advantages of the invention include the following:
1. Integration of combustion facilities with greenhouse gasxe2x80x94solidifying fertilizer production reactionsxe2x80x94conversion of CO2, CO, SOx, and NOx. emissions into carbonate-containing fertilizers (primarily, ammonium bicarbonate and urea);
2. Sequestration of CO2 by enhanced carbonation of soil and subsoil terrains through the application of the carbonate-containing fertilizers;
3. Enhancement of photosynthetic fixation of CO2 from the atmosphere by the technology-driven production of carbonate-containing fertilizers.
This invention utilizes waste heat from combustion facilities and converts various industrial waste gases, including CO2, CO, H2, CH4, N2, NH3, NOx, and SOx, into commercial products, primarily fertilizers. It has the capability to solidify as much as 90% of the CO2 from flue gas and place the carbonate-containing fertilizers into soil and subsoil earth layers, which at the same time can reduce NO3xe2x88x92 contamination of surface water and groundwater. Based on the current annual world consumption of nitrogen fertilizers, as much as 315 million tons of CO2 per year from smokestacks could potentially be placed as bicarbonate into soil by worldwide use of this invention. In addition, this invention has the potential to remove CO, SOx, and NOx emissions and to enhance photosynthetic fixation of CO2 from the atmosphere. Therefore, the invention also has significant value in improving energy efficiency, enhancing economic competitiveness, and reducing environmental impacts of both the fossil energy system and the fertilizer industry.